It has been a long time goal of the thermal management community to have a method to remove high thermal energy loads without the use of large surface area heat exchangers. Conventional designs of cooling products such as vapor compression based refrigeration systems; all use the same basic components to accomplish cooling or heating. Over the long history of refrigerant based vapor compression systems, only incremental advancements in the technology have been made resulting in relatively small increases in system efficiency and effectiveness. While compressors are more efficient, evaporator and condenser heat exchangers are only incrementally better and as such the basic technology has progressed rather slowly over the last 70 years.
If one looks at these basic components, some inherent inefficiencies become apparent quickly. Consider a typical condensing coil unit. It is generally a large array of finned tube coils through which a fan either pulls air across or pushes air over. The finned coils are fairly efficient at exchanging thermal energy with airflow, but considerable work must be performed to provide adequate airflow across the coils for significant heat exchange. No matter how efficient the exchanger may be, thermal energy must be removed from the system. In an air cooled system the volumetric airflow required for proper heat transfer is significant.
In general terms, the capacity of a heat exchanger is directly proportional to its surface area. It is also proportional to the temperature and volume of air flowing across its exposed surface area. These and other factors must be considered when designing an efficient exchanger.
When considering the state of the art in heat exchanger technology, in large part, inefficiency revolves around the movement of air and air mover technology utilized for thermal exchangers. Whether a blower, tube axial fan, bladed fan or some other structure is utilized, the process of air movement is extremely inefficient ranging from a low of 6 percent to a high of 60 percent, depending on method and size. If one includes one or more electric motors into the efficiency calculation, the overall efficiency drops to 50 percent at best. To compensate for these inefficiencies, exchanger systems are designed to be larger and heavier.
One solution to these issues is proposed by U.S. Pat. No. 3,020,025 which is directed to a heat exchanger that is adapted to be rotated during operation and particularly to a device in the form of a double hollow shaft assembly having a number of fins or paddles spaced there along including fins which may be selectively adjusted as to angular inclination and fins which employ a substantial portion of their volume for circulation of heat exchange fluid therein.
As can be seen from the disclosure contained in U.S. Pat. No. 3,020,025, the heat exchanger disclosed therein utilizes fin assemblies that have one or more pipes located along the center line of a fin assembly, where such one or more pipes are able to contain a heat transfer fluid. While the heat exchanger of U.S. Pat. No. 3,020,025 seeks to increase the operating efficiency thereof, this heat exchanger device suffers from a number of drawbacks. For example, if one were to use the design of U.S. Pat. No. 3,020,025 to create a heat exchanger where a high rate of rotation was required by the fin assemblies disclosed therein, such high rate of rotation would cause pooling of the heat transfer fluid at the end of the fin assemblies due in part to the centrifugal forces created by a high rate of rotation.
Accordingly, given the above, a need exists in the art for a rotary heat exchanger with improved system efficiency.